The flavor SU(4) quark model predicts 22 charmed baryons [1]}, [2]}, but many of them are not yet discovered.
They are one triply charmed baryon \(\Omega _{ccc}\)  and five doubly charmed baryons of \(\Xi ^+(ccd)\) , \(\Xi ^{++}(ccu)\) , and \(\Omega _{cc}(ccs)\)  with spin 1/2 or 3/2.
Searching for doubly charmed baryon \(\Xi ^+(ccd)\)  in the experiment lasts for decades. The SELEX collaboration [3]} claimed the observation of \(\Xi _{cc}^+\)  in the channel \(\Xi _{cc}^+\rightarrow \lambda _c K\pi \)  in 2003, but the Belle [4]}, BaBar [5]} and LHCb [6]} collaborations failed to reproduce the results in the same or other decay channels.
In 2017, the LHCb Collaboration observed the \(\Xi _{cc}^{++}\)  in the \(\Lambda K\pi ^-\pi ^+\)  decay channel [7]}. And the mass is around 3621.4 MeV which is consistent with theoretical predictions [8]}, [9]}, [10]}, [11]}, [12]}, [13]}, [14]}, [15]}. Their production cross-sections in proton-proton [16]} and heavy-ion collisions [17]} are also studied and show the cross-section is significantly enhanced in heavy-ion collisions [17]}.
The quark model can be derived from the theory of quantum chromodynamics (QCD) which allows many fantastic color-singlet hadrons, such as Glueballs [19]}, [20]}, multi-quark states (e.g. tetraquarks and pentaquarks) [21]}, [22]}, hybrids [23]}, [24]}, and hadronic molecules [25]}, [26]}. The discovery of charmonium (bottomonium)-like exotic states which named XYZ mesons, especially the recently discovered fully-heavy tetraquark state \(X(cc\bar{c}\bar{c})\)  [27]} attract much attention of experimenters and theorists.
